1. Field of the Invention
The present invention relates to a cleaning method of a ceramic member.
2. Description of the Related Art
In general, a ceramic member is processed by, for example, a diamond tool in the final stage of the manufacturing process. In the process stage with the diamond tool, the debris accompanying the processing, the diamond abrasive grains, etc. (hereinafter referred to as an “extraneous material”) are attached to the surface of the ceramic member, with the result that various detrimental effects are generated during use of the ceramic member. Particularly, where the ceramic member is used in the manufacturing process of a semiconductor device or in the manufacturing process of a liquid crystal display device, it is possible for the extraneous materials to be attached to the semiconductor wafer or to the liquid crystal substrate as particles so as to give rise to defects. Such being the situation, it is necessary to completely remove in advance the extraneous materials attached to the ceramic member.
It should also be noted that it is absolutely necessary in recent years to employ the process step using a highly corrosive fluorine series or chlorine series gas or a plasma in the manufacturing process of a semiconductor device or in the manufacturing process of a liquid crystal display device. Particularly, in the manufacturing process of a semiconductor device, these corrosive gases or the plasma are frequently used in the steps of, for example, the chemical vapor deposition (CVD), the dry etching and the cleaning of the chamber. Under the circumstances, the members exposed to the corrosive gas atmosphere or to the plasma atmosphere during the process steps noted above are required to exhibit a high corrosion resistance to the corrosive gas and the plasma. In compliance with the requirement, a ceramic material such as an alumina sintered body, sapphire or an aluminum nitride sintered body is used for forming the members which are to be exposed to the corrosive gas atmosphere or to the plasma atmosphere.
However, even in the case of using such a ceramic member under the corrosive gas atmosphere or under the plasma atmosphere, a chemical reaction is generated between the ceramic member and the corrosive gas or the plasma, with the result that the surface of the ceramic member is contaminated with the reaction product. The reaction product noted above is present on the surface of the ceramic member as particles, or the particular reaction product is directly formed on the surface of the ceramic member. Since the reaction product in question renders the plasma state unstable or causes the semiconductor device, which is being manufactured, to be contaminated, it is necessary to remove the reaction product appropriately.
A chemical method is employed for removing the extraneous materials attached to the surface of the ceramic member in the manufacturing stage of the ceramic member. To be more specific, the ceramic member is cleaned with a chemical liquid for removing the extraneous materials by allowing the extraneous materials to be dissolved in the chemical liquid. On the other hand, for removing the reaction product formed by the reaction between the ceramic member and the corrosive gas or the like, which contaminates the ceramic member during the manufacturing process of the semiconductor device or the liquid crystal display device, employed is a physical method in which the reaction product in question is physically removed by polishing the surface of the ceramic member or a chemical method in which the particular reaction product is removed by allowing the reaction product to be dissolved in a chemical liquid. Japanese Patent Disclosure (Kokai) No. 2003-55070 discloses a chemical method of removing the extraneous materials and the reaction product which are hereinafter referred to as a “contaminant”. It is taught that a ceramic member contaminated with the contaminants is processed with an alkaline chemical liquid and, then, with an acidic chemical liquid, followed by applying a prescribed heat treatment to the ceramic member.
However, a rapid progress is being made in recent years in, for example, the semiconductor device in respect of the miniaturization of the circuit pattern and the degree of integration. As a result, the ceramic member, which is satisfactory when used in the manufacturing process of the conventional semiconductor device, brings about a difficulty when used in the manufacturing process of the latest semiconductor device. In other words, a difficulty is generated even in the case where the amount of the contaminants remaining on the ceramic member is lowered to reach such a low level as not to give detrimental effects to the manufactured semiconductor device when the ceramic member is used in the manufacturing process of the conventional semiconductor device. To be more specific, it is possible for the contaminants attached to the ceramic member to bring about inconveniences when the ceramic member is used in the manufacturing process of the latest semiconductor device. For example, it is possible for the yield of the manufactured latest semiconductor device to be lowered. Under the circumstances, it is of high importance to develop a cleaning method that permits removing with a higher accuracy the contaminants attached to the surface of the ceramic member so as to further decrease the residual amount of the contaminants.